1. Technical Field
This invention relates generally to pistons for heavy-duty diesel engine applications, and more particularly to a method of forming pistons in which the skirt is united with the piston body as a one piece structure.
2. Related Art
Pistons for heavy-duty diesel applications include an upper head formed with a ring belt having pin bosses depending therefrom for connecting the piston to a connecting rod of an engine. Such pistons also include a piston skirt that is formed either integrally as one piece with the head and pin boss portions known as a xe2x80x9cmonoblocxe2x80x9d piston, or formed as a separate movable structure which is coupled in articulated fashion to the pin bosses by a wrist pin.
In monobloc pistons, the skirt is typically either cast or forged as one piece with the piston body and of the same material. Casting or forging the skirt as one piece with the piston body thus limits the material that can be used for the skirt and also limits the design options of the skirt to those capable of being either forged or cast with the piston body.
A piston constructed according to the present invention overcomes or greatly minimizes the above limitations of prior methods of making monobloc pistons, and particularly with respect to the formation the skirt.
A method of manufacturing a piston for heavy-duty diesel engine applications comprises forming a piston body having a pair of pin bosses, and bonding separately formed skirt portions to the pin bosses. The resultant piston has the separately formed skirt portions united to the piston body in a monobloc piston construction.
One advantage offered by this method of making a piston is the ability to form the skirt by stamping or rolling separately from the formation of the piston body, which may be cast or forged as usual. Forming the skirt in this fashion simplifies the construction and manufacture of monobloc pistons and lowers the cost.
Another advantage of the invention is that stamping or rolling of the skirt portions provides for a thin wall construction, contributing to a lighter piston assembly. The thin-walled skirt portions may also be elastically flexible to minimize scoring or marking of the cylinder walls.
Another advantage of the invention is that the opposing skirt portions may be fabricated to different specifications such that the skirt on a non-thrust side of the piston may have a thinner and lighter skirt portion than that on the thrust side.
Another advantage of the invention is that the skirt portions can be manufactured from any of a number of materials and are not limited to those used to form the piston body. In this way, the materials most suitable for the piston body and skirt can be separately selected and joined through bonding to provide optimum performance of both the piston body and skirt portions for a given application.